1. Field of the Invention
The present invention is directed to the reclamation of aluminum or aluminum alloy swarf and a method of treating the reclaimed swarf to enable the same to be extruded either alone or with a conventional billet of cast aluminum to provide a composite aluminum product.
2. Prior Art
In aluminum casting or machining workshops there is a considerable amount of particulate waste or swarf of aluminum or aluminum alloy which is produced as a result of cutting, grinding or boring operations. A dissolution method is available to reclaim this waste but such a method suffers from an extremely low rate of recovery due to the oxidation to which a major portion of the aluminum particles is subjected.
Several attempts have been made to compress such aluminum particles into billets within a metalic mold but such attempts are not satisfactory for producing products of consistent quality due to a considerable amount of foreign matter such as oxides and abrasive particles present in the waste as well as cutting oil and cutting materials which are extremely difficult to remove from the waste. Furthermore, prior art attempts to extrude such billets by forcing the billets under pressure through a die orifice to produce extruded products were generally unsatisfactory. Such extruded products frequently had reduced mechanical strength due to the presence of pores in the billets which resulted from a poor bond or insufficient fusion between the particles. The presence of such pores furthermore resulted in extremely poor finish on the extruded material.
Several prior art attempts have also been made to provide a composite extruded product having a core and a covering layer. One of these methods for producing such a composite product is a hot rolling pressure welding method. This method is advantageous in that it permits a continuous operation but the products are necessarily limited to a round-shaped and its equivalent. The other method is a hydrostatic extrusion method such as that disclosed in ASEA: Wire Ind, 38, 647 (Sept. 1971) N. Hornmark, D. Frmel: Draht-Welt 56, 424 (Aug. 1970). This method involves the production of copper clad aluminum products by hydrostatic extrusion wherein a composite billet comprising a preformed core of aluminum surrounded by a close fitting sheet of copper is subjected to hydrostatic pressure through a pressure medium in response to the travel of a ram. When the pressure reaches a predetermined value the composite billet is forced through a die orifice into a predetermined shape. Thus, no friction occurs between the billet and the container in which the billet is placed and furthermore a forced lubrication effect is provided by the pressure medium between the die and the billet resulting in an extremely low friction loss. Although this method only permits an intermittent operation as distinct from the aforementioned rolling method it is highly efficient in that a high degree of formability is available for a cold operation as compared to the conventional method and that elongated billets are usable. In other words, according to this hydrostatic extrusion process, there is no limitation as to the shape of the products. However, this hydrostatic extrusion process requires the use of hydrostatic extrusion equipment and also a coating material in the form of a tubing. The formation of such a composite billet wherein a preformed billet of pure aluminum is provided with a close fitting sheet of copper prior to extrusion is an extremely costly and troublesome operation.